mineral

Agate

Silicon Dioxide (SiO2) - Variety of Chalcedony

Hardness: 6.5–7 on Mohs scale; Color: Multi-colored bands (gray, brown, white, tan); Luster: Waxy to vitreous; Crystal structure: Hexagonal (cryptocrystalline); Cleavage: None; Specific Gravity: 2.58–2.64.

Hardness: 6
Color: Multi-colored bands (gray, brown, white, tan)
Luster: Waxy to vitreous

Identified March 16, 2026More mineral →

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Physical properties

Formation & geological history

Formed in cavities of igneous rocks or ancient lavas. Silica-rich groundwater percolates through vesicles (gas bubbles), depositing thin layers of microcrystalline quartz over thousands of years. Ages range from millions to over a billion years old.

Uses & applications

Primary use in lapidary arts for jewelry (cabochons, beads), ornaments, and decorative handles. Due to its hardness and chemical resistance, it is also used industrially for precision pendulums, mortars and pestles, and laboratory equipment.

Geological facts

The name 'Agate' comes from the Achates River in Sicily, where it was first discovered in ancient times. Every agate is unique; no two specimens have identical banding patterns, which are caused by periodic changes in the silica concentration and mineral impurities during formation.

Field identification & locations

Identify by looking for translucent edges, waxy luster, and distinct concentric or moss-like banding patterns. Common in volcanic regions and riverbeds; notable locations include Brazil, Uruguay, Lake Superior (USA), and India.

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Epidote

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metamorphic

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

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